Your first injection: what it is actually like

The first shot is a two-minute task that people spend a week worrying about. This page is the two minutes, plus the three days after.

Before you open the box

1. Check the strength. The first box should be the initiation dose on your prescription: 0.25 mg for Wegovy or Ozempic, 2.5 mg for Zepbound or Mounjaro (section 2.1 of each label). If the box says anything else, call before injecting.
2. Read the Instructions for Use once, all the way through. Every device is different. They are on DailyMed under each product (links below) and in the carton.
3. Take it out of the refrigerator early. The labels allow the pens to be used straight from the fridge, but cold liquid stings more. Unopened Wegovy pens may be kept at room temperature (8 to 30°C) for up to 28 days; Zepbound pens up to 21 days at up to 30°C (section 16). Do not freeze either.
4. Pick the site. Abdomen (at least two inches from the navel), front of the thigh, or back of the upper arm (section 2). Rotate each week. Not into a bruise, scar or hard lump.
5. Pick the day and write it down. Same day each week. Wegovy allows the day to be changed as long as two doses are at least 48 hours apart; Zepbound requires at least 72 hours (section 2).
6. Read the when to call page now, so you know the difference between ordinary nausea and a symptom that needs a phone call.

Pens

Wegovy comes as a single-dose pen with the needle hidden. You remove the cap, press the pen firmly against the skin, and hold; the Instructions for Use say to keep pressing until the yellow bar in the window has stopped moving. There is nothing to dial. The used pen goes in a sharps container.

Zepbound and Mounjaro come as single-dose autoinjector pens. You pull off the base cap, place the base flat on the skin, unlock, press and hold the button; the Instructions for Use describe two clicks, the first when the injection starts and the second when it is complete, over up to about 10 seconds. Zepbound is also sold in single-dose vials you draw up with a syringe (see below).

Ozempic is a multi-dose pen with a separate needle you attach each time. You do a flow check on a new pen, dial the prescribed dose, insert, press and hold while counting slowly to 6, then remove and dispose of the needle. Never share a pen even with a new needle (section 5, risk of transmission of blood-borne pathogens).

In every case: clean the site with an alcohol swab and let it dry, do not rub afterwards, and put sharps in a proper container, not the household bin.

Compounded vials

Compounded semaglutide or tirzepatide usually arrives as a multi-dose vial and a bag of insulin syringes. Compounded products are not FDA approved and are not interchangeable with the brand pens, and this is the moment that difference is most concrete: you are measuring the dose yourself.

• The vial label gives a concentration, such as milligrams per millilitre. Your prescription gives a dose in milligrams. The number you need is the syringe units for that dose at that concentration. Work it out with the dose unit converter, then compare with what the pharmacy wrote. If the two disagree, stop and call the pharmacy.
• FDA has received reports of people drawing up five to twenty times the intended dose because they confused units with millilitres or milligrams. Read the check before you inject guide before the first draw.
• Swab the vial top, draw air into the syringe equal to the dose, inject the air into the vial, then draw the liquid and tap out bubbles. Injection technique from there is the same as a pen: pinch, insert at the angle the pharmacy showed you, press the plunger fully, withdraw.
• Ask the pharmacy or your prescriber to watch the first draw on video if you can. It takes five minutes and catches most errors.

The first three days

Blood level peaks one to three days after a semaglutide dose and 8 to 72 hours after a tirzepatide dose (section 12.3). If you are going to notice anything from a first dose, it is usually in that window: a smaller appetite, feeling full earlier, sometimes mild nausea or burping. Many people notice nothing at all at the initiation dose, which the labels describe as a starting dose to reduce gut side effects rather than a treatment dose. Both are normal. Drink normally, eat smaller portions if you are full, and do not skip fluids because you are not hungry (hydration).

What is not normal in the first days is severe abdominal pain, vomiting that does not stop, signs of an allergic reaction, or any thought of harming yourself. Those are on the call list with the label wording next to them.

Then

Put the next injection in your calendar seven days out. The week-by-week planner will do that for the first 12 or 20 weeks and attach what to expect to each date. Weeks 1 to 4 is the next page.